By Emily Swaim
The curve on the sole of your foot, called an arch, helps keep your foot in alignment as you walk. A strong arch maintains your foot’s shape when you put pressure on it, ensuring no one part of your foot gets overworked.
Flat feet don’t have a stable arch. While some people function just fine with flat feet, others have a lot of pain and difficulty walking. Your outcome depends a lot on whether you have anatomically flat feet or acquired flat feet (collapsed arches).
Types of Flat Feet
All humans come out of the womb with flat feet. Infants have a pad of fat on their soles as cushioning, so unlike an adult’s footprint that “disappears” around the arch, a baby’s footprint will be full all the way through. This trait is called developmental flatfoot, and it’s a normal part of infancy.
What are Anatomically Flat Feet?
As a child grows and starts walking, their feet will develop the tissues necessary to create an arch. Almost half of kids will grow an arch by age 3, and nearly three-fourths will grow an arch by age 6.
However, 15% of people never develop a fully-formed arch, so their feet stay flat. This condition has a number of names, including anatomically flat feet, physiological flatfoot, and pediatric flexible flat feet (PFFF).
What are Collapsed Arches?
Most people develop arches and keep them for a long time. But aging, disease, or overuse can damage the structures supporting your foot’s arch, causing it to collapse. Usually your arch flattens gradually, but an injury could make your arch crumble all at once.
This condition is called progressive collapsing foot deformity (PCFD). Before 2020, experts often called it adult acquired flatfoot deformity (AAFD), though teenagers can get it too. While physiological flatfoot affects both feet at once, it’s possible to have a collapsed arch in only one foot.
Signs and Symptoms of Flat Feet
In general, anatomically flat feet cause fewer health issues than collapsed arches.
When are Anatomically Flat Feet an Issue?
Most kids with pediatric flexible flat feet don’t have symptoms like pain or trouble walking. Anatomically flat feet are almost always flexible, meaning the arch only goes flat when you put weight on it. You may not realize you have flat feet until someone else points it out.
That said, between 7%-15% of adults with anatomically flat feet develop symptoms that need medical attention. You may want to visit a doctor if you have:
How Do You Know if Your Arch Collapsed?
A collapsed arch can cause very mild symptoms, or it could lead to severe disability, depending on the kind you have. According to a 2022 study, 58.7% of people with PCFD have flexible flat feet, 5.5% have rigid flat feet, and the rest (35.8%) have some combination of flexibility and rigidity.
In general, flexible flat feet give you milder symptoms. You may have pain and swelling around your ankle, as well as pain along your arch. You may also have difficulty with high-impact exercises like jogging, but be able to walk easily so long as you have supportive footwear.
As PCFD progresses, the pain gets worse, and your condition becomes more visible. You may notice that when you stand, your ankle juts out to the side instead of sitting straight under your calf. Your front foot may splay outward to compensate.
Late-stage PCFD usually results in rigid flat feet—this means your arch stays flat all the time, whether you have weight on it or not. Rigid feet are often so painful and stiff they affect your ability to move around. You might not be able to bend your foot enough to follow through a step and push off the ground. Standing on your tiptoes often becomes impossible.
What Causes Flat Feet?
Flat footedness can happen for a variety of reasons.
What Causes Anatomically Flat Feet?
Some people inherit anatomically flat feet from their parents. You are more likely to inherit this condition if you are male or if you have very flexible joints (hypermobility).
Other people don’t inherit flat feet directly, but they do have genetic conditions or health issues that affect their foot shape. For example, Marfan syndrome or Ehlers-Danlos syndrome can affect connective tissue throughout your body, including the tissues supporting your arch.
What Causes Arches to Collapse?
As you get older, the tissues in your feet see a lot of wear and tear. That’s why arch collapse tends to happen in mid-life and later life. Among people aged 65 and over, 10% have experienced collapsed arches. The condition is more common among women than men.
Similar to anatomically flat feet, acquired flat feet can happen due to underlying health issues such as arthritis. However, the most common cause of arch collapse is damage to your posterior tibialis tendon (PTT). This tendon does most of the work holding your arch up, so if it swells or tears, all the other support structures in your foot quickly become overloaded, and your arch will likely fall down.
Treating Flat Feet
Because anatomical flat feet and acquired flat feet have different origins and outcomes, their treatment often differs too.
Addressing Anatomically Flat Feet
Around 10% of American children with anatomically flat feet use orthotics, or devices which adjust the fit of their shoe.
However, experts disagree on whether treatment is necessary or effective. Some studies say foot orthoses can improve your limb alignment when walking. Other research suggests issues involving flat feet go away as children age, regardless of their footwear.
Generally doctors don’t recommend treating anatomically flat feet unless you have chronic pain or difficulty walking. You can use home remedies like stretching and ice to relieve any temporary discomfort and stiffness.
Can You Fix Collapsed Arches?
You can’t exactly rebuild a collapsed arch, but treatment can reduce a lot of your symptoms. The earlier you catch the issue, the easier it is to address.
Stretching and supportive footwear can help strengthen collapsed arches. Orthotics and inserts for flat feet are effective too, and they can keep your arch from degrading to the point where you need surgery.
ANATOMICALLY FLAT FEET
Affect both feet
Affect one or both feet
Most common in male children
Most common in middle aged women
Almost always flexible
Over 40% of cases have some rigidity
Usually causes no symptoms
Can be mild, moderate, or severe
Often caused by genetics or health issues present at birth
Often caused by damage to your posterior tibial tendon
Orthotics and insoles generally not necessary
Insoles and orthotics are a common therapy